Mankind is constantly searching for new drugs to cure its afflictions. Of all of mankind's ills none has engendered a greater effort to find new drugs than cancer. The long, and largely fruitless, search for new and more effective treatments for cancer has led many scientists to reconsider the long-held belief that chemists could derive effective anti-tumor compositions merely by trial and error in the laboratory. These scientists have realized that nature provides a far greater variety of medicinal compounds synthesized by plants than could ever be made at the laboratory bench. Thus, attention has turned to the jungles and forests of the world as a storehouse of new and effective anti-tumor compounds. For example, the drug Taxol, found in the Pacific Yew, has a structure few medicinal chemists would have derived a priori. Yet, this compound has shown strong anti-tumor properties.
Several important anti-tumor compounds have been isolated from microorganisms. For example, bleomycin A.sub.2 and B.sub.2 are produced by Streptomyces verticulls. These compounds are used in the treatment of testicular cancer, squamous cell carcinoma, and Hodgkin's disease. Dactinomycin, isolated from Streptomyces antibioticus, has been used successfully against choriocarcinoma, Wilms tumor and testicular tumors. Cyclosporine, a metabolite of Cylindrocarpon lucidum and Trichoderma polysporum is an immunosuppressive and is effective against severe aplastic anemia. Thus, microbes continue to be a source of effective anticancer compounds.